Melting experiments of a chondritic meteorite between 16 and 25 GPa; implication for Na/K fractionation in a primitive chondritic Earth's mantle

Melting experiments were conducted at 16-25 Ga using the M'bale (L6) chondrite plus added Na and K, and gave majorite garnet with enhanced amounts on Na (Na (sub 2) O 3.75-4.71 wt%) and moderately enhanced K (K (sub 2) O 0.3-0.46 wt%). It is the Na- and K-bearing phase over this pressure range. At pressures above 21 GPa, majorite, magnesiowustite and perovskite are produced; the Na (sub 2) O content of magnesiowustite progressively increases with increase of pressure, whereas for majorite and perovskite it is negatively correlated with pressure between 23 and 25 GPa. The hollandite-structured high-pressure KAlSi (sub 3) O (sub 8) crystallizes from the liquid at 23 GPa. At P > 21 GPa Na/K fractionation should have taken place in the early accretional period in the primitive chondritic mantle of the Earth.